GEEEN RIVER EOCENE. 241 



1,200 feet^ of calcareous shales, of white and brown colors, so thinly and 

 regularly laminated that they have been called paper-shales. Within the 

 shales are intercalated thin arenaceous beds, whose proportion increases in 

 descending, while the base of the series is formed of more or less calcareous 

 sandstones of white and buff color, and earthy impure limestones, with local 

 developments of lignite. The upper member consists of a bed of about 

 100 feet in thickness of coarse brown sandstone, of massive structure, which 

 caps the bluffs in the neighborhood of Green River City, where it seems to 

 have been hardened by local metamorphism so as to have preserved from 

 erosion the underlying, more easily-disintegrated beds. In Plate VI, which 

 represents two peculiar tower-like columns about 150 feet in height pro- 

 jecting from the summit of the hills back of Green River City, the summit 

 of the columns is seen to be formed of the massive sandstone, their base 

 being in these peculiar fissile shales. The best exposures of the shales are 

 found at the base of these bluffs, and in the railroad cuts, about four miles to 

 the. west of Green River City, and along the valley of Bitter Creek, to the 

 east. From the shale beds at these localities immense quantities of fish 

 remains have been obtained, together with a few fossil insects. Among 

 the fishes j although individuals are so abundant, the number of species dis- 

 covered is thus far comparatively limited. As described by Professor 

 Cope,^ the genera Clujaea, Asineops, Erismatopterm, and Osteoglossum are 

 represented. In their affinities, they are closely allied to the Eocene Tertia- 

 ries of Monte Bolca in Italy. The living representatives of the latter 

 genus inhabit generally fresh waters of warm, equatorial regions, while the 

 presence of the first named, whose modern representatives are the herrings, 

 indicate a probable connection of the sea with salt- waters. 



The following species have been described from these beds : 



nSHES. 



Clupea humilis, Leidy. 

 Clupea alta, Leidy. 

 Clupea fusilla, Cope. 

 Osteoglossum encaustum, Cope. 



16 D G 



1 Geological Survey of the Territories, 1870. 



